1. Field of the Invention
The present invention relates to a projector assembled such that an image display device such as a liquid-crystal panel is integrally held around a prism for composing or decomposing light beams.
2. Description Related to the Prior Art
It is well known three-panel type liquid-crystal projectors which decompose the white light into red light, green light, and blue light, modulate the three color light to an image light by using image display devices corresponding to respective color light, and then compose the three color image lights and project the composed image light. For example, in a three-panel type liquid-crystal projector having liquid-crystal panels of transmissive type, a cross-dichroic prism having two dichroic surfaces which are orthogonal to each other composes three color light beams having passed through each liquid-crystal panel. The cross-dichroic prism has a rectangular solid shape, and each liquid-crystal panel is disposed so as to face each of three side surfaces of the cross-dichroic prism. A composed light beam enters a projection lens from a remaining side surface of the prism to which the liquid-crystal panel did not face. In addition, as disclosed in Laid-Open United States Patent Application 2003/0189676, it is known a three-panel type liquid-crystal projector in which light beams decomposed by a polarizing beam splitter enter liquid-crystal panels of reflective type disposed so as to face side surfaces of the polarizing beam splitter.
To assemble these types of projectors, it is known that the liquid-crystal panels are integrally held with an optical element having the rectangular solid shape, such as the cross-dichroic prism and the polarizing beam splitter. For example, to eliminate the use of frames to be adhered to side surfaces of a prism, U.S. Pat. No. 6,587,167 discloses fixing pins having a flat surface at one end to be adhered to a side surface of a prism, and a liquid-crystal panel with holes, in which the fixing pins are inserted. The liquid-crystal panel is fixed to the prism such that between the hole and outer peripheral surface of the fixing pin, and between the flat surface of the fixing pin and the side surface of the prism are respectively adhered by adhesive agent. As another example, in Japanese Patent 3360804, a liquid-crystal panel is screwed or adhered to an upper holder and a lower holder which are fixed on upper and bottom surfaces of a prism, instead of fixing the liquid-crystal panel directly to the side surface of the cross-dichroic prism as the conventional method.
However, in the above described prior arts, because the bottom surface of the cross-dichroic prism is adhered directly to a base plate, an adhesive layer formed in between can be uneven in thickness. In this case, the prism does not stand upright but lean to any side on the base plate. Accordingly, light beams exit from the prism are distorted. In this state, proper projection performance cannot be obtained even if a position of the liquid-crystal display for attaching to the prism is changed. To obtain the proper projection performance, there are needs to detach the base plate and the liquid-crystal panels from the prism to which they are adhered, and to reassemble these disassembled components. This process consumes considerable time.